In this paper, a numerical method is presented to solve the two-dimensional two-phase steam flow over a series of geometries (such as nozzles, expansion corners and steam turbine blade-to-blade passages) by means of equilibrium thermodynamics model. The flow is assumed to be compressible and inviscid and obeys the ideal gas equation of state. The resulted equations are then numerically solved by the Roe’s FDS time marching scheme that has recently been modified to allow for two-phase effects. Validations of condensing steam flow through vapor nozzles have been performed, where good agreement has been achieved. Detailed parametric studies monitoring the influence of (I) the geometry expansion rate, (II) the inlet total temperature and pressure, and (III) the expansion fan or shock waves on the location of condensation onset and the rate of condensation are given. Finally as a case study, expansion of steam flow through a steam turbine blade-to-blade passage is considered, and condensation or evaporation of the steam flow through the passage and fate of the wet flow through the fan or shocks were observed.

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